quick temper
A tendency to become angered, enraged, or upset very quickly or easily. I'm usually a pretty calm person, but whenever I start driving I find I have such a quick temper.
have a quick ˈtemper
become angry easily: Just be careful how you tell him — he’s got a very quick temper and he’s quite scary when he’s angry! ▶ ˌquick-ˈtempered adj.: She’s quite a quick-tempered woman.